This invention relates to the ejection of materials from a mold, and, more particularly, to the completion of ejection of molded structures at the end of the molding cycle.
In the molding of structures, for example by injection molding, thermoplastic material is forced into patterned recesses of a separable mold. After the material has been injected into the recesses, the sections of the mold are separated and ejector pins are operated in an attempt to force the molded structure from the recesses of the mold. In high speed molding operations, the ejector pins are not always successful in freeing the structure from the mold.
Accordingly, to assure the complete ejection of molded structures, it is a common practice to employ a device such as a mold wiper, which is synchronized with the operation of the machine and assists the ejector pins by "wiping" the structure from the mold at the end of each molding cycle. The typical mold wiper is mounted at the top of one of the sections and includes a plate that is moved downwardly when the mold separates. Since the downward motion is generally inadequate to complete the ejection, the plate is also propelled forwardly.
Conventional devices for the wiping of molds are complex and intricate. The use of a downwardly moving plate adds significant bulk. In addition the need for forward motion, once the plate is in position, adds an extra dimension of complexity to the machine.
Because of the intricacy, complexity and cost of mold wiping equipment, the completion of mold ejection in many installations take place manually with the operator reaching into the opening between mold portions. This is, of course, objectionable because of the hazards presented to the operator.
Accordingly, it is an object of the invention to facilitate the separation of molded structures from mold cavities at the end of each molding cycle. A related object is to simplify the separation of structures from mold cavities.
Another object of the invention is to avoid the need for complex and combersome wiping machinery in order to separate molded structures from mold cavities. A related object is to eliminate the need for separate downward and forward motions of the wiper in order to bring about the desired completion of mold ejection.
A further object of the invention is to achieve the completion of mold ejection without requiring manual intervention while not significantly adding to the complexity of the molding operation.